1. Field of the Invention
The present invention relates to techniques for cooling electronic devices, and more particularly to a technique for applying the principle of jet heat transfer in cooling the surface of electronic devices.
2. Description of the Related Art
In general, various types of electronic devices, such as CPUs (Central Processing Unit) for controlling electronic products or DSPs (Digital Signal Processor), are made up of various electronic components including active elements such as transistors or passive elements such as capacitors. These electronic components are driven by electric energy, part of which is converted into heat energy to be dissipated. Since the performance of the electronic components typically depends on the temperature, this dissipated heat has adverse effects on the performance of the electronic components and thus on the electronic device. Accordingly, the electronic device cooling technology is extremely critical to providing proper control to electronic devices.
As an example of cooling techniques, there is available a cooling method using an electric fan. In this method, the electric fan is situated opposite to a surface of an electronic device. The electric fan allows cooler air introduced through an air inlet to impinge on the surface of the electronic device. The air heated by absorbing heat generated on the surface of the electronic device is exhausted through an air exhaust outlet. In this manner, heat generated on the surface of the electronic device is removed by the electric fan, thereby cooling the electronic device.
As another example, there is also available a method of cooling electronic devices using cooling water. In this method, the surface of the electronic device is covered with a water-proof case so that cooling water passes the surface of the electronic device. The cooling water heated by absorbing heat generated on the surface of the electronic device is drained through a cooling water drain outlet. In this manner, heat generated on the surface of the electronic device is absorbed by the cooling water, thereby cooling the electronic device (see, for example, Japanese Patent Laid-Open Publication No. 2002-026555 and Japanese Patent Laid-Open Publication No. 2001-221529)
Recent electronic devices tend to increasingly produce larger amounts of heat due to their higher-speed operations, further improved functions, and higher packaging densities. This tendency is now overwhelming the conventional cooling methods that employ air or liquid, making it more difficult to sufficiently cool those electronic devices.
From a macroscopic point of view, the aforementioned conventional cooling methods focus on how to remove heat generated on the surface of electronic devices. However, from a microscopic viewpoint, heat is not uniformly produced on the surface of an electronic device. In general, the electronic components constituting an electronic device are grouped in modules for particular functions. Accordingly, the distribution of heat generated on the surface may vary depending on the processing performed by the electronic device. This is because the electronic device has to provide different functions.